1. Field of the Invention
The present invention relates generally to a method and apparatus for connecting two or more fluid carrying tubes. More particularly, it relates to a method and apparatus for connecting blood carrying medical tubing in a continuous fluid circuit without introducing bubbles or other environmental contaminants into the tubing.
2. Description of the Prior Art
Extracorporeal procedures are well known. In these procedures, blood generally is withdrawn from a patient through cannulation, treated (e.g. by pumping, oxygenation, filtering, or the like), and reintroduced to the patient through cannulation. For example, in a cardio-pulmonary bypass procedure, blood may be withdrawn through cannulation at a first site, oxygenated upstream, and reintroduced through cannulation at a second site.
In preparing to perform one of these extracorporeal procedures, one blood carrying tube must be connected to another blood carrying tube. It is important in making this connection to avoid introducing air or other contaminants into the fluid circuit. In particular, air bubbles can cause an embolism or other medical complications that may be fatal to the patient.
Before initiating an extracorporeal procedure, each of the blood carrying tubes typically is primed with a conventional priming fluid, such as a saline-based priming solution, and then clamped at a location proximate the end portion thereof, to assure that each is filled as full as possible with such fluid. The open ends of the primed tubes are then slowly connected together while a syringe or other device provides a continuous stream of solution to the connection site. A variation of this technique may be used when the fluid circuit includes a roller-type pump. In this variation, a perfusionist rotates the pump head of the pump in a forward direction to perform a "roll-up" technique, which continuously advances priming fluid out of the blood tube during the connecting stage.
These techniques have a number of drawbacks. First, each technique requires a degree of training to make a bubble free connection. For example, in the former technique, connection under a stream of fluid may cause air entrainment, resulting in bubbles in the tubing. The latter technique is limited to a roller-type pump, and may not be used with a centrifugal pump, or the like. Each of these techniques requires two people to perform the connection. In addition, since these procedures rely upon flowing fluid to keep air out, they tend to be messy since some of that flowing fluid necessary escapes from the system. Also, after completion of the connection, it often is not possible to disassemble the cannula and tubes if bubbles then are detected in the tubes. Moreover, these techniques are not easily repeatable, and are difficult to perform under emergency conditions.
It is also known in the art to use a connector tube for connecting the open ends of two-fluid carrying tubes. Such a connector tube preferably is a short, rigid cylindrical tube, and may include securing structure, such as barbs, at each end for securely connecting the previously open ends of the fluid carrying tubes to form a closed fluid channel or circuit.
An improvement on this technique includes a hard, barbed, connector tube provided with a branch or side-arm luer port. The luer port may be used for collecting and eliminating any air bubbles trapped in the fluid circuit after connection.
These techniques also have a number of drawbacks. Initially, when a connector tube is inserted in the open end of one fluid carrying tube, it functions as an extension of that tube for connecting to the second tube. Thus, this system includes all of the above-discussed drawbacks. The branches or luer fittings also have a drawback in that they introduce an element that protrudes from the fluid circuit during procedure. This protrusion may catch on surrounding objects or accidentally be broken off, resulting in inconvenience or possibly major blood loss during procedure. Moreover, these protrusions form vestiges that remain on the side wall of the connector tube of the fluid circuit. These vestiges are discontinuities that form stagnation zones in the fluid circuit that tend to cause thrombi.